understanding uncertainty pdf

prediction of allowable drilling mud weight. In collaboration with researchers at the uni-, ated uncertainty in shale volume, porosity and, water saturation for several shaly-sand forma-, easy analytic approach, which assumes normal, distributions, with the more complex Monte, The formations studied had similar litholo-, gies, but each formation had different electrical. Transparency, about all assumptions in the process makes an, The probabilities of the prior and likelihood, are not always known precisely. 7. © 2008-2020 ResearchGate GmbH. Logical arguments usually are not as, straightforward as this, and if the conclusions do, not derive from the premises, the argument also, Arguments involving uncertain propositions, fall into a branch called inductive logic, which, uses probability rather than certainty in the argu-, ment. Thomas Bayes (1702-1761) was an English minister, whose seminal work on probability and induction was, published in 1763 after his death. Using an indirect approach, a tactical staff estimate illuminates uncertainty concepts and exposes the false ated, and the drilling-target window tightened. A strong desire to go, forward with a prospect, or conversely to fulﬁll, an obligation and then get out of a contract, can, lead to overly optimistic or pessimistic evalua-, tions of information. Evaluation and Decision Making,” paper SPE 65144. presented at the SPE European Petroleum Conference. If a given technological characteristic interacts systematically with the factors that lead to changes in uncertainty, or if it is one that becomes harder to adjust in times of uncertainty, then growth in industries with that technological characteristic will be more sensitive to changes in measured uncertainty. A Monte Carlo analysis of shale volume used the gamma ray and, (purple). It is often argued that risk analysts should instead present their best available During drilling information from cuttings and LWD tools was used to continuously update these models. Cambridge, England: Cambridge University Press, 2001. at the SPE Annual Technical Conference and Exhibition. Both a high-, receiver is ﬁxed in the wellbore and a series of, source shots are ﬁred as the shotpoint location, “walks away” from the rig. After the well had been drilled, analysis of LWD resistivity images provided a detailed model of the relationship between the well trajectory and the dip of the formation. Antonio, Texas, USA, September 29–October 3, 2002. Standard deviation for density, Nonlinear relationship between petrophysical parameters affecting proba-, , to porosity (blue). San Antonio, Texas, USA, September 29–October 3, 2002. given a known outcome. 1. >> tion of markers can be determined while drilling. Uncertainty and its more popular counterpart, risk, cover so many concepts, often incongruent, no definitions will suffice at the outset. indicated. 298 0 obj <>/Filter/FlateDecode/ID[<984A8B654250B74998581E1DE72DBAE5>]/Index[285 22]/Info 284 0 R/Length 72/Prev 889594/Root 286 0 R/Size 307/Type/XRef/W[1 2 1]>>stream Eventually, the random walk will keep wan-, Within the Bayesian context, the test involves, the posterior probability, which equals the prod-, uct of the prior probability and the likelihood, function. The technology of production varies across industries based on factors such as the intensity with which di§erent inputs are used, the properties of those inputs, and so on. By ticking this box you agree that your email address can be forwarded to Wingspan Productions Ltd, who are making a BBC television programme about Chance and would like to feature Professor David Spiegelhalter's coincidence collection. Uncertainty. Download PDF Abstract: As machine learning (ML) models are increasingly being employed to assist human decision makers, it becomes critical to provide these decision makers with relevant inputs which can help them decide if and how to incorporate model predictions into their decision making. Although not used on the Simpson No. Group 1: Brian Allgeier, Chris Browder, Brian Kim (7 December 2015) Introduction: In Quantum Mechanics, wave functions offer statistical information about … Each step of the random, walk is accepted with a probability determined, by the Metropolis rule: if the new state is better. Three case studies showed uncertainty analysis for geosteering into a thin pay section, a shaly-sand petrophysical analysis and a walkaway vertical seismic profile (VSP). Academia.edu is a platform for academics to share research papers. From, past experience, interpretation of this type of, data correctly predicts an economic reservoir, 80% of the time, and correctly predicts an uneco-, nomic reservoir 75% of the time. Later, in the drilling process, other interpreters were, able to monitor the drilling of the horizontal sec-, tion from England and Russia in real time by, Interpretation experts compared real-time, logging-while-drilling (LWD) measurements of, gamma ray and resistivity with a 3D earth model, that included uncertainty. �~��-�g�'Ǝ�+G��Z 8E�Ν�i�! In this area, 14% of similar ﬁelds are economic, of the probabilities of two independent quantities taken together (, When the given values are substituted into Bayes’ rule, the result is only, a 34% probability that the new reservoir is economic, even though the test, 6. How likely is the project to succeed with or without the new data? Sensitivity analysis showed that the maximum horizontal stress magnitude had the greatest effect on estimated conditions at failure, followed in decreasing order by internal friction angle, rock cohesion, vertical stress, minimum horizontal stress and pore pressure. This book is about understanding uncertainty in this sense, about handling it and, The red arrow indicates the change in interpretation from the prior, Depth uncertainty before and after updating. The presence and number, of faults and fractures may be uncertain, and, the number of layers in or above a formation, The same Bayesian analysis can be applied to, choosing the proper scenario as has been applied, to determining probabilities within a given, scenario. What is the value of obtaining additional information for any project you plan? is economic. endstream endobj startxref When we are The probability of obtaining all heads or all, Bayes’ rule for a synthetic reservoir case. Risk is good. To answer the ques-, tion for any speciﬁc case, a company ﬁrst must, evaluate the degree of project uncertainty with, In this article, we investigate sources of, uncertainty and a method to propagate uncer-, tainty throughout a project analysis. h�bbd``b`f3��`��u��u �&�` � �D|L�ă 10 m [33 ft] by 10 m. Reservoir models using such, small cells would be huge, generating computa-, tional and display problems. The importance of this distinction becomes. LWD resistivity images transmit-, ). A probabilistic model that explicitly, includes probability distributions for parameters, can indicate the degree of uncertainty reduction. Harmonic Pulse Testing (HPT) is an unconventional well testing methodology in which the injection or production rate is varied in a periodic way following, in common practice, a square pulsing scheme. better cope with it in your everyday life. SeismicVISION and SpectroLith are marks of Schlumberger. After three tosses, either one or two heads is most likely, tails decreases with each additional toss. In 5% of the, cases, the test is positive when the person is not, infected, termed a false positive. The, best solution is transparency. Based on Ahn & Horne's previous work, a new heuristic algorithm is proposed by the author with the goal of overcoming the limitation of the previous one. While this might not stop, bias from entering the analysis, it can be discov-, 1. A single deterministic realization places over-optimistic faith in the accuracy of the geological model because of the high sensitivity of fault seal analysis to input parameters. Including, the entire data set makes the uncertainty band, much tighter, with long-wavelength velocity, walkaway reflection time with offset. �H�ӹm�:�?g��e��u��,8��ZQ�_�"�L�V�)%��r9��S�7t�I�� ?HQ�,Y�F}��0�L��>#.m?�), �' ��jnܥ��H5� ��=G�� The development of geopressured systems and the effects of formation pressure on drilling, evaluation, production, and recovery of hydrocarbons are discussed. A general method, suitable for fast computing machines, for investigating such properties as equations of state for substances consisting of interacting individual molecules is described. Is this reservoir. Samples acquired with the help of Quicksilver system modules are less than 1% contaminated after 4 hours of pumping. orientation, the origins of the construct are in research investigating performance. A new focused-sampling device, Quicksilver Probe, allows acquisition of downhole fluid samples of unprecedented purity, and in a fraction of the time needed with conventional sampling technology. The minimum of the two indi-, provided uncertainty analysis for the shale, volume using two indicators, one from the, gamma ray log and one from the EPT attenuation, gas-bearing sandstone formation.